A conventional method is described in European Patent Application No. 0 285 419 which allows a querying unit to unequivocally recognize one allocated transponder from a group of several transponders allocated to the querying unit. To do so, the querying unit progressively checks the codes of the transponders present in the access region of the querying unit. The codes are configured as multi-digit binary words. In a first query step, the querying unit checks their first digit to determine whether it matches the first digit of a reference code word present in the querying unit. All transponders which do not match at the first digit no longer participate in further testing. The remaining transponders which match at the first digit are then checked, in a second query step, as to whether the second digit of their code words agrees with the second digit of the reference code word in the querying unit. The procedure is repeated until a single transponder, whose binary coding matches all the digits of the reference code in the querying unit, is identified. For unequivocal determination of one among 2n transponders, this procedure requires n query steps. Its effect of selecting one specific qualified transponder from a plurality of transponders qualifies the known apparatus for access protection applications, in particular for situations in which sufficient time is available for performing the recognition method. In practice, however, it is often demanded that the allocation of a remote controller to a relevant base station take place in the shortest possible time, for example in the case of access systems for opening or locking doors. It is the object of the present invention to describe an allocation apparatus which permits an unequivocal allocation of an actuation element to a base station at high speed, while guaranteeing sufficient security.
The object is achieved by a method and by apparatuses configured for performing this method. The method according to the present invention advantageously eliminates any delay in ascertaining the allocation by the fact that the base station periodically delivers search signals which, when an allocated remote controller is present, initiate an allocation dialog without further user intervention. Advantageously, emission of the search signals is accomplished with little energy outlay using a corresponding energy-intensive carrier signal, while the subsequent allocation dialog, on the other hand, uses a carrier signal which guarantees secure communication. The remote controller is accordingly designed so that it is fundamentally in. an idle state which it departs from only when a search signal enters it. The method according to the present invention allows delay-free allocation even if multiple base stations are arranged in physical proximity, and if the effective ranges of their search signals overlap. In an embodiment suitable for this purpose, the base station has a device for receiving search signals from third-party base stations. Taking into account any third-party search signals being emitted, it transmits its own search signals in such a way that overlaps are prevented. Advantageously, an apparatus according to the present invention further provides a possibility for execution of an allocation test dialog to be initiated by a user.